A 1.2 V low-power OpAmp for integrated lock-in amplifiers

This paper presents a simple 1.2 V low-power rail-to-rail class AB operational amplifier (OpAmp) suitable for integrated lock-in amplifiers. The proposed OpAmp has been designed in a standard 0.18 mu m CMOS technology. For a 1.2 V single supply and 68.6 mu W power consumption, simulations shows a 81 dB open loop gain, 64 degrees phase margin, 13 MHz unity gain frequency for a capacitive load of 10pF and 75 dB CMRR. Adaptive biasing provides 30.7 V/mu s slew-rate for a 10 pF load. A compact and reliable lock-in amplifier (LIA) has been designed using the proposed circuit. The designed LIA has a power consumption of 135 mu W and recovers signals up to 1 MHz with relative errors below 2.6 % for noise and interference signals of the same amplitude as the signal of interest.